In this paper I present a framework for the conceptualization of languages based on the prototype theory of categorization proposed by Eleanor Rosch and her colleagues for natural semantic categories. It is motivated by research in the Casamance region of southern Senegal, where a high level of multilingualism in non-standardized varieties is the norm, making accurate description of languages, and thus analysis of multilingual discourse, problematic. I show that languages in this context can be conceived of as categories, of which linguistic features may be more or less prototypical members. Such an approach can form the basis for a more robust method of language description, integrating rich sociolinguistic data, and facilitating more nuanced analysis of multilingual discourse data.